Before committing the code into the repository I wanted to make
sure it is the correct way to fix it.

The first change changes the callback to orte_rml_send_callback().
When I initially made the code compile again I used hnp_receiver()
to change the code from blocking to non-blocking and that was
wrong.

The second change (removal of OBJ_RELEASE(buffer)) is necessary
because this seems to delete buffer during communication and then
everything breaks badly.